Hammer mechanism for percussion tools

ABSTRACT

This invention relates to a hammer mechanism for percussion tools provided with a hammer piston for delivering blows to a percussion implement, and further provided with a hammer element arranged movable relatively to said hammer piston, said hammer piston being stopped during the upward movement thereof by said hammer element for delivering the kinetic energy of said hammer piston to said hammer element.

United States Patent lnventor Eero Antero Erma Klinten, Sweden Appl. No. 821,554 Filed Apr. 30, 1969 Patented Mar. 16, 1971 Assignee Atlas Copco Aktieholag Nacka, Sweden Priority May 8, 1968 Sweden 6221/68 HAMMER MECHANISM FOR PERCUSSION TOOLS 6 Claims, 4 Drawing Figs.

U.S. Cl 173/116, 173/122, 173/139 Int. Cl 825d 9/10, B25d 11/06 Field of Search 173/ 122, 133, 116, 139

[56] References Cited UNITED STATES PATENTS 1,060,647 5/1913 Steinbach 173/122 2,121,706 6/1938 Little 173/122 2,239,090 4/1941 Everett 173/122 Primary Examiner.lames A. Leppink Att0rneyEric Y. Munson ABSTRACT: This invention relates to a hammer mechanism for percussion tools provided with a hammer piston for delivering blows to a percussion implement, and further provided with a hammer element arranged movable relatively to said hammer piston, said hammer piston being stopped during the upward movement thereof by said hammer element for delivering the kinetic energy of said hammer piston to said hammer element.

PATENTED HARI 6 I97! sum 2 or a Fig. 219V 7 I INVEN'I'OR. 42m Ania/0 Er'vnd PATENTED m 1 s IBYI SHEET 3 BF 3 Fig. 3

3 HAMMER MECHANISM FOR llERCUSSION TQOLS This invention relates to a hammer mechanism for percussion tools of the type having a working piston which by means of a pressure medium in a working chamber for said piston drives a hammer piston which transmits its kinetic energy to a percussion implement. The invention is particularly applicable to portable rock drills driven by internal combustion engines, but may also be utilized in conjunction with other types of hammer mechanisms irrespectively of the nature of the power source.

in a known hammer mechanism for an internal combustion engine-driven rock drill the combustion gases drive the rock drill hammer piston directly, the hammer piston and a captive engine piston being arranged in one cylinder, in which the hammer piston absorbs as kinetic energy the energy liberated by the combustion process. After having delivered a blow to a percussion implement the hammer piston returns towards the internal combustion engine piston by action of a superatmospheric pressure in a chamber positioned below the hammer piston. However, the return velocity and the length of the return stroke of the hammer piston is also at least partially dependent upon the hardness of the material to be treated by the percussion implement and the recoil from the percussion implement and the material to be treated. This implies that the hammer piston is not always in proper position relatively to the engine piston when combustion starts, and this happens especially when the material to be treated has varying hardness. The result is uneven running of the engine.

The position of the spark plug in said known rock drill is an additional drawback, since said spark plug has to be positioned in the sidewall of the combustion chamber, resulting in an unsymmetrical combustion chamber and a disadvantageous combustion process causing incomplete combustion. Thus, the engine speed has to be limited to a low value, which is disadvantageous with regard to the output.

One object of the invention is to provide a hammer mechanism for percussion tools which eliminates said recoil drawbacks and which may be operated at a considerably higher number of revolutions than has been possible in conventional portable rock drills, particularly in those driven by internal combustions engines.

The hammer mechanism according to the invention is characterized by a hammer member arranged to be movable relatively to said hammer piston in the direction of motion thereof, a first abutment in the hammer mechanism which limits the movement of the hammer member in a first direction, a return motion chamber for the hammer piston in which a pressure medium acts on the hammer piston in a second opposite direction, means for biasing said hammer member towards a resting position on said first abutment when the hammer piston delivers a blow to said percussion implement, a second abutment on the hammer member, and a third abutment on the hammer piston arranged to cooperate with said second abutment so that when the hammer piston has delivered a blow the hammer piston is moved in said second direction by the pressure medium in said return chamber until said third abutment engages the second abutment, the mass of the hammer member being so dimensioned relatively to the mass of the hammer piston as to cause the hammer piston motion in the second direction to stop when the third abutment engages the second abutment and the kinetic energy of the hammer piston is delivered to the hammer member, so that the hammer piston always attains well-defined and positions in the hammer mechanism irrespective of the magnitude of the recoil from the percussion implement and the material to be treated.

In a preferred embodiment the hammer is a hammer ring which concentrically encloses and slidably cooperates with the hammer piston and together with the hammer piston defines the return chamber, the pressure medium in said return chamber forming the means for biasing the hammer member.

A great advantage of the hammer mechanism according to the present invention lies above all in the fact that the number of revolutions of the hammer mechanism or the number of blows of the hammer piston may be optimized so that the greatest possible amount of working energy may be delivered per time unit by the hammer mechanism which has not been possible when using previously known machines because of the low maximum number of blows thereof.

The foregoing and other objects and advantages of the invention will be more apparent as the specification proceeds. in the accompanying drawings one embodiment of a rock drill provided with a hammer mechanism according to the invention is illustrated by way of example together with diagrams illustrating the operation of said hammer mechanism.

FIG. 1 is a side view partially in section of a rock drill provided with a hammer mechanism according to the invention. FIG. 2A and 2B are diagrams illustrating the hammer piston and the hammer ring movement, respectively, as a function of time between uppermost and lowermost piston and ring positions. FIG. 3 is a diagram illustrating the total impact energy per minute as well as the impact energy per blow as a function of the number of blows of the hammer piston or the number of revolutions of the engine.

The rock drill illustrated in FIG. 1- cornprises a conventional internal combustion engine provided with a cooling fins l, a cylinder 2, a piston 3, a spark plug 4, a connecting rod 5, a flywheel 27, and a crank shaft 6. A connecting rod 7 for a compressor or working position 8 reciprocable in a compressor cylinder 9 is journaled on the crank shaft the direction of the connecting rod 7 being opposite that of the connecting rod 5. An inlet opening 10 for air to a compression chamber 11 is provided in the wall of the cylinder 9. The pressure in said chamber ranges between 0 and l5 atmospheres gauge, for instance. The compression chamber ll is limited downwards by a hammer piston 32, a hammer ring 13 being arranged concentrically around the hammer piston and serving as an auxiliary piston for the hammer piston. A return chamber 14 is disposed concentrically between the hammer piston i2 and the hammer ring 13, said return chamber having permanently a superatmospheric pressure ranging between about I and L5 atmospheres gauge, for instance. Compressed air is supplied to the return chamber for the chamber ll, for instance through the clearance around the hammer piston 12. The hammer ring 13 is fitted in the casing 21 of the hammer mechanism which provides a seat 18 forming a first abutment for the hammer ring 13. The hammer ring l3 has an internal annular flange 16 which forms a second abutment cooperating with a third abutment formed by an external annular flange 15 on the hammer piston 12. The hammer ring 13 forms a seal with the hammer piston at 19. The hammer ring flange l6 during the upward movement of the hammer piston is engaged by the third abutment formed on the hammer piston flange 15. The hammer piston is guided in the casing 21 at 17. The first abutment 18 limits the downward motion of the hammer ring T3. The hammer ring 13 has a cylindrical guiding and sealing surface 20 which cooperates with a bore in the casing 2! of the hammer mechanism. Flushing air is supplied to a flushing duct 25 in a drilling implement 22 through passages 23 and 24 as indicated by arrows or through a passage. in the hammer piston. A drill sleeve and a rotary driver 26 are arranged for the drill steel rotation.

The operation of the rock drill with the hammer mechanism according to the invention will now be described. in HO. 1 the engine piston and compressor or working piston are shown in their uppermost positions in the cylinders, i.e. in the positions near the crankshaft. The engine piston 3, by means of the kinetic energy stored in the flywheel 27, compresses the fuelair mixture in the cylinder 2 for the succeeding combustion. Simultaneously, the compressor piston 8 compresses the air in the compression chamber ill from atmospheric pressure to about 15 atmospheres gauge. The hammer piston 12 begins its downward movement in the cylinder 9 when the pressure in the compression chamber exceeds 1 atmosphere guage, due to the superatmospheric pressure of about 1 atmosphere gauge which exists in the return chamber M and which opposes said downward motion. A little later the hammer ring returns to the first abutment 18 after having been thrown upwards by the hammer piston during the upward movement of the hammer piston in the preceding working stroke. As the hammer piston proceeds downwards it is accelerated as a result of the increasing compression in the chamber 11 and reaches a velocity of about meters/sec. when delivering the blow to the drill steel or implement 22. The pressure in the compression chamber 11 has then already dropped from a maximum value of about 7 l5 atmospheres gauge to a few atmospheres gauge. The pressure in the return chamber 14 is then about l.5 atmospheres gauge the pressure increase being caused by the fact that the hammer ring 13 is stopped against the abutment 18 before the hammer piston delivers the blow to the drill steel. During the downward movement of the compressor piston 8 flushing air is conducted from the compression chamber 11 through the ducts 23, 24 or 29 down into the flushing duct 25 in the drill steel 22.

At about the same time as the hammer piston delivers the blow to the drill steel the combustion process takes place in the engine cylinder 2, the compressor piston 8 is thereby forced upwards. The hammer piston begins its upward movement when the pressure in the compression chamber 11 has dropped below 1.5-atmospheres gauge. During the upward movement of the hammer pistonthe third abutment on the flange engages the second abutment on the flange R6 of the hammer ring 13 which was at rest on the first abutment 118. The masses of the hammer piston and the hammer ring are so mutually dimensioned as to ensure that the hammer piston always stops when striking the hammer ring irrespectively of the magnitude of the recoil from the drill steel and the material to be treated by the drill steel, whereas the hammer ring continues upwards thereby compressing air in a chamber 28 formed between the flange l6 and the cylinder. The ring 13 travels upwards a distance which is partially dependent on the magnitude or the recoil. The hammer ring then returns into engagement with the abutment 18 when the hammer piston has again started its downward movement during the succeeding working stroke. Thus, the initial position of the hammer piston is always the same at the beginning of each stroke.

The time-position diagram for the hammer piston and the hammer ring in FIG. 2A and 28, respectively, illustrates how the hammer piston when moving upwards strikes at its uppermost position the hammer ring, which is resting in its normal or rest position and which thereby is thrown upwards, then reaches its uppermost position and returns to its normal position waiting for the succeeding stroke of the hammer piston, before the hammer piston has reached its lowermost position, i.e., the position when the blow is delivered to the drill steel. The hammer piston stops against the hammer ring and the hammer piston remains in this uppermost position during a time interval which is somewhat shorter than the time required for the up-down movement of the hammer ring. Thus, the hammer piston has its normal or rest position at the uppermost point of its motion whereas the hammer ring has its normal or rest position at its lowermost point.

FIG. 3 is a diagram illustrating how the total impact energy E per time unit and the impact energy e per stroke varies as a function of the number of blows of the hammer piston. By varying the distance a between the compressor piston and the hammer piston in their uppermost positions the impact energy 2 per stroke may be varied as well as the total impact energy E. The total impact energy E may be optimized by proper choice of the distance a. The optimum is not reached when the impact energy e per stroke has its maximum but at a somewhat greater number of blows, as is obvious from FIG. 3. This high number of blows has not been possible to reach in prior forms of hammer mechanisms of this type having the hammer piston driven directly by means of the combustion gases in the cylinder of an internal combustion engine. The optimizing of the impact energy per minute is of great advantage and is made possible by the hammer ring which serves as an auxiliary hammer piston.

The invention is not limited to the embodiment described and shown or to the mentioned values of superatmospheric pressure, piston velocity and length of piston stroke but may be modified within the scope of the claims.

lclaim:

l. A hammer mechanism for a percussion tool, particularly for a portable rock drill of the type having a working piston which by means of a pressure medium in a working chamber for said piston drives a hammer piston which transmits its kinetic energy to a percussion implement, said hammer mechanism having a hammer member arranged movably relatively to said hammer piston in the direction of motion thereof, a first abutment in the hammer mechanism which limits the movement of the hammer member in a first direction, a return motion chamber for the hammer piston in which a pressure medium acts on the hammer piston in a second opposite direction, means for biasing said hammer member towards a resting position on said first abutment when the hammer piston delivers a blow to said percussion implement, a second abutment on the hammer member and a third abutment on the hammer. piston arranged to cooperate withsaid second abu tmentso that when the hammer piston has delivered a blow the hammer piston is moved in said second direction by the pressure medium in said return chamber until said third abutmentengages the second abutment, the mass of the hammer member being so dimensioned relatively to the mass of the hammer piston as to cause the hammer piston motion in the second direction to stop when the third abutment engages the second abutment and the kinetic energy of the hammer piston is delivered to the hammer member, so that the hammer piston always attains well-defined end positions in the hammer mechanism irrespective of the magnitude of the recoil from the percussion implement and the material to be treated.

2. A hammer mechanism according to claim 1, in which the hammer member is a hammer ring which concentrically encloses and slidably cooperates with the hammer piston and together with the hammer piston defines the return chamber, the pressure medium in said return chamber forming the means for biasing the hammer member.

3. A hammer mechanism according to claim 1, in which the hammer mechanism has a casing in which an annular seat is provided for said hammer ring, said seat forming the first abutment, an internal annular flange on the hammer ring forming the second abutment, and an external annular flange on the hammer piston forming the third abutment.

4. A hammer mechanism as defined in claim 1, in which the working piston constitutes a compressor piston driven by a crank shaft having an internal combustion engine piston journaled thereon, the compressor piston and the engine piston being joumaled on opposite cranks of said crankshaft.

5. A-hammer mechanism as defined in claim 1, in which the distance between the hammer piston and the working piston in their uppermost positions is chosen so as to optimize the blow energy per time unit at a predetermined number of blows of the hammer mechanism.

6. A hammer mechanism for a percussion tool and particularly for a portable rock drill of the type having a working piston which by means of a pressure medium in a working chamber for said piston drives a hammer piston which transmits its kinetic energy to a percussion implement, the hammer piston having a hammer ring arranged concentrically around it and acting as an auxiliary piston for the hammer piston, a casing in which the hammer ring is fitted, said casing having a seat forming a first abutment for the hammer ring, the hammer ring having an annular flange forming a second abutment, said second abutment cooperating with a third abutment formed by an annular flange provided on the hammer piston, the flange on the hammer ring being engaged by the third abutment during the upward movement of the hammer piston and the first abutment limiting the downward movement of the hammer ring. 

1. A hammer mechanism for a percussion tool, particularly for a portable rock drill of the type having a working piston which by means of a pressure medium in a working chamber for said piston drives a hammer piston which transmits its kinetic energy to a percussion implement, said hammer mechanism having a hammer member arranged movably relatively to said hammer piston in the direction of motion thereof, a first abutment in the hammer mechanism which limits the movement of the hammer member in a first direction, a return motion chamber for the hammer piston in which a pressure medium acts on the hammer piston in a second opposite direction, means for biasing said hammer member towards a resting position on said first abutment when the hammer piston delivers a blow to said percussion implement, a second abutment on the hammer member and a third abutment on the hammer piston arranged to cooperate with said second abutment so that when the hammer piston has delivered a blow the hammer piston is moved in said second direction by the pressure medium in said return chamber until said third abutment engages the second abutment, the mass of the hammer member being so dimensioned relatively to the mass of the hammer piston as to cause the hammer piston motion in the second direction to stop when the third abutment engages the second abutment and the kinetic energy of the hammer piston is delivered to the hammer member, so that the hammer piston always attains well-defined end positions in the hammer mechanism irrespective of the magnitude of the recoil from the percussion implement and the material to be treated.
 2. A hammer mechanism according to claim 1, in which the hammer member is a hammer ring which concentrically encloses and slidably cooperates with the hammer piston and together with the hammer piston defines the return chamber, the pressure medium in said return chamber forming the means for biasing the hammer member.
 3. A hammer mechanism according to claim 1, in which the hammer mechanism has a casing in which an annular seat is provided for said hammer ring, said seat forming the first abutment, an internal annular flange on the hammer Ring forming the second abutment, and an external annular flange on the hammer piston forming the third abutment.
 4. A hammer mechanism as defined in claim 1, in which the working piston constitutes a compressor piston driven by a crank shaft having an internal combustion engine piston journaled thereon, the compressor piston and the engine piston being journaled on opposite cranks of said crankshaft.
 5. A hammer mechanism as defined in claim 1, in which the distance between the hammer piston and the working piston in their uppermost positions is chosen so as to optimize the blow energy per time unit at a predetermined number of blows of the hammer mechanism.
 6. A hammer mechanism for a percussion tool and particularly for a portable rock drill of the type having a working piston which by means of a pressure medium in a working chamber for said piston drives a hammer piston which transmits its kinetic energy to a percussion implement, the hammer piston having a hammer ring arranged concentrically around it and acting as an auxiliary piston for the hammer piston, a casing in which the hammer ring is fitted, said casing having a seat forming a first abutment for the hammer ring, the hammer ring having an annular flange forming a second abutment, said second abutment cooperating with a third abutment formed by an annular flange provided on the hammer piston, the flange on the hammer ring being engaged by the third abutment during the upward movement of the hammer piston and the first abutment limiting the downward movement of the hammer ring. 